Various methods have been used heretofore to put the human brain into a Theta (below 7 Hz.) or Alpha (7-14 Hz.) brain wave state.
The Alpha state of the brain is considered desirable as promoting relaxation of the body, reducing or eliminating anxiety or mental stress, enhancing the brain's efficiency and creativity, and promoting a feeling of peace and silence.
The Theta state of the brain is associated with peaceful sleep.
In considering the possibility of using conventional magnetic tape recordings to induce the Theta or Alpha state, the first, seemingly insuperable problem is the low frequency limit of conventional tape recording/playback instruments. Those in the low price range (e.g., below $60) typically are not designed for frequencies below 200 Hz. Those in an intermediate price range (e.g., $95-175) typically can handle frequencies down to about 70 Hz. Even tape recorders/players in the price range above $1,000 cannot adequately record or reproduce signal frequencies below 20 Hz.